Multifocal visual evoked potential recordings in compressive optic neuropathy secondary to pituitary adenoma

To investigate the effect of pituitary adenoma compressing the optic chiasm on multifocal visual evoked potential (mfVEP) responses and to compare these responses with visual field defects seen on static automated perimetry (SAP). Eight eyes of four subjects (median age, 41.50 years; interquartile range, 33-51 years) who were diagnosed with pituitary adenoma on magnetic resonance imaging (MRI) and seen to have a bitemporal visual field defect on standard automated perimetry (SAP), and twelve age-matched normal subjects (median age, 47.00 years; interquartile range, 34.75-51.75 years) were subjected to multifocal visual evoked potential (mfVEP) testing. The monocular latencies and monocular amplitudes of each sector of cases were compared with the responses of normative database. The topography of the mfVEP response was compared with corresponding field defect as seen in total deviation threshold on SAP to allow a comparison with conventional subjective perimetry. The mfVEP amplitudes were reduced in the areas with visual field defect on SAP. In 6 out of 8 eyes, locations with preserved amplitudes and no visual defects showed prolonged latency. A prolonged median latency of 9.17 ms (interquartile range, 3.44-17.69 ms) in cases was seen when compared to the median latency of 1.67 ms (interquartile range, 0.94-4.17 ms) in age-matched controls with P value of 0.054. Chiasmal compression due to pituitary adenoma causes the reduction of amplitudes and prolongation of latencies of the mfVEP response. The mfVEP can be used to assess objectively the topography of the visual field in compressive optic neuropathy secondary to pituitary adenomas. It can be used in assessing the subjects whose visual field report is unreliable and prolonged median latency can be an early sign of the disease.